Formation degradation, such as asphalt milling, mining, or excavating, may result in wear on attack tools. Consequently, many efforts have been made to efficiently remove and replace these tools.
U.S. Pat. No. 6,371,567 to Sollami, which is herein incorporated by reference for all that it contains, discloses a bit holder with its mating bit block utilizing a slight taper in the bit block bore, and a tapered shank on the bit holder that includes a second larger diameter tapered distal segment that combines with an axially oriented slot through the side wall of the bit holder shank to allow a substantially larger interference fit between the distal tapered shank segment and the bit block bore than previously know. When inserting the bit holder in the bit block bore, the distal first tapered segment resiliently collapses to allow insertion of that segment into the bit block bore. A second shank tapered portion axially inwardly of the first distal tapered portion and separated therefrom by a shoulder provides a space between the bit block bore and the second tapered shank portion until the upper ⅛ to ½ inch of the second tapered shank portion meets and again forms an interference fit with the bit block bore at a portion of the shank above a termination of the slot therethrough. The dual tapered shank allows the insertion of the bit holder in the bit block with an interference fit that provides a secure mounting of the bit holder in the bit block. Since there is no fastener to maintain the bit holder in the bit block, it may be removed from the bit block by driving the base of the bit holder out of the bit block.
U.S. Pat. No. 7,210,744 to Montgomery, Jr., which is herein incorporated by reference for all that it contains, discloses a wear sleeve comprising a rearward split ring portion and an intermediate cylindrical ring portion adjacent a forward shoulder portion. The outer diameter of the wear sleeve intermediate portion and rearward split ring portion is uniform. The wear sleeve is inserted into the bit holder's stepped bore aperture. The split ring portion is radially compressed by the smaller diameter opposite portion end as the sleeve is hammered and axially displaced into the bit holder. The split ring portion forms frictional contact with the opposite end portion of the aperture. The wear sleeve friction fit can b easily removed manually in the field. The bit holder and cooperation support block are designed to limit the amount of relative yaw between the two members during operation to reduce the overall wear there between. The invention includes a groove having side surfaces that are inclined at least 15 degrees with respect to the horizontal axis and the cutting bit is positioned more apt toward the central axis of the support block than prior art designs.